Composer package name in unexpected format

Composer 1.9.0 is complaining about package name:

Deprecation warning: Your package name drupal-contrib:media_entity_twitter is invalid, it should have a vendor
name, a forward slash, and a package name. The vendor and package name can be words separated by -, . or _. T
he complete name should match "[a-z0-9]([_.-]?[a-z0-9]+)*/[a-z0-9]([_.-]?[a-z0-9]+)*". Make sure you fix this
as Composer 2.0 will error.

We have settled on drupal/ as the namespace for contrib.